To add a sticky note (text annotation) to a PDF Document.

async function main() {
    const doc = await PDFNet.PDFDoc.createFromURL(filename);
    const page = await doc.getPage(1);

    // Create the sticky note (Text annotation)
    const txt = await PDFNet.TextAnnot.create(doc, new PDFNet.Rect(10, 20, 30, 40));
    await txt.setIcon("UserIcon");
    await txt.setContents("The quick brown fox ate the lazy mouse.");
    await txt.setColor(await PDFNet.ColorPt.init(0, 1, 0));
    await txt.refreshAppearance();
    await page.annotPushBack(txt);
}
PDFNet.runWithCleanup(main);

Add or edit PDF annotations
Full code sample which shows how to add or edit PDF annotations (e.g. hyperlink, intra-document link, stamp, rubber stamp, file attachment, sound, text, free-text, line, circle, square, polygon, polyline, highlight, squiggly, caret, and ink).